MRI findings in patients with acute coronary syndrome and unobstructed coronary arteries

PURPOSE The underlying diagnosis in patients with acute coronary syndrome (ACS) and unobstructed coronary arteries remains a diagnostic challenge. We analyzed the value of magnetic resonance imaging (MRI) in this clinical setting. METHODS A total of 213 patients with ACS and unobstructed coronary arteries underwent MRI within a median of 2 days after initial presentation. Clinical, laboratory, and MRI data were analyzed. A consensus diagnosis was established for each case by an independent panel after reviewing the individual clinical, laboratory, and MRI data. Standardized interviews to determine patient outcomes were carried out after a median follow-up of 24 months. Clinical events were defined as a composite of death, stroke, myocardial infarction or recurrence of Takotsubo syndrome (TTS), new onset of heart failure with a left ventricular ejection fraction (LVEF) <30%, and occurrence of a new left ventricular thrombus formation. RESULTS Final diagnoses included acute myocardial infarction (AMI) (40%), acute myocarditis (24%) and TTS (33%). In 3% of patients, nonspecific findings lead to an indeterminate diagnosis. Patients with TTS showed a significantly impaired LVEF during the index event (50% vs. 60% in AMI and 60% in myocarditis, P = 0.001). The extent of myocardial edema was most pronounced in patients with TTS (13.4%±11.4 vs. 4.6%±7.9 in AMI and 1.8%±2.7 in myocarditis, P < 0.001). TTS patients had the highest event rate (16.9%). CONCLUSION Our study emphasizes the diagnostic utility of timely MRI in patients with ACS and unobstructed coronary arteries. We found a high prevalence of TTS patients, who had poorer outcomes compared with patients with a final diagnosis of AMI or myocarditis.